In the present study, some important limitations need to be considered. First, sleep parameters were obtained in absence of objective sleep time; although this limit is insurmountable due to the obvious impossibility of measuring these parameters in absence of electrophysiologic signals, we calculated the polygraphic indices following the recommended method for cardiorespiratory monitoring.32 Second, chronic sleep duration (CSD) was not assessed and, therefore, there is the possibility that there were between-group differences with regard to CSD, such that ESSs and ESSp scores differed on this basis rather than, or in addition to, the manner of instrument administration. However, the exclusion from this study of several conditions that commonly affect CSD, such as shift work,33 psychiatric and neurologic diseases,34 and related drugs,34 may, to some extent, counterbalance this limitation. Third, the study conditions regarding the ESSs may not reflect all clinical environments. Indeed, in our study, participants in group 1 were left alone in the waiting room and were not permitted to ask questions after beginning the questionnaire; we suspect that most clinical environments allow confused patients to ask questions. It is important, however, to underline that our study stems from the desire to make evident and clear what, to date, is only a suspicion: The questionnaire completed with the help of a physician is more accurate than the ESSs. Another limitation of this study is represented by a small sample size. Therefore, larger trials are requested to confirm our finding. In addition, it would be of interest to know if longitudinal reproducibility differs between ESSs and ESSp.